We built this while working on our own Mac/iOS app (QW Code Viewer) the core highlighting engine as a standalone library.
Key points:
Written entirely in Swift (no Python runtime or bindings
Currently supports ~20 programming file formats
Designed for Mac & iOS usage
Includes unit tests + visual regression tests
PNG and PDF outputs are verified using OCR(tesseract) to ensure the rendered syntax highlighting is actually correct (not just pixel-diffed)
The OCR testing was added because we wanted confidence that exported images/PDFs still preserve semantic correctness after rendering. Also because it was vibe coded.
This is our first OSS release in this space.
Happy to answer questions and learn from the community.